Rectal cancer is a type of bowel cancer that develops in the last several centimeters of the large intestine, just before the anus. It’s one of the most common cancers in Europe, with over 125,000 people diagnosed annually. Treatment traditionally involves surgery to remove the tumor—a major operation that can permanently affect sexual function, continence, and quality of life.
While radiotherapy and chemotherapy are already used to shrink tumors before surgery, there is growing momentum behind treatment strategies that avoid surgery in patients, where the tumor has disappeared after radiotherapy and chemotherapy. Such so-call “organ preservation strategies” aim to preserve the rectum, and thereby maintain a better quality of life for cancer patients—especially for early-stage and locally advanced cases.
In contrast, anal cancer affects the lowest few centimeters of the bowel. It is a rare disease and is diagnosed in around 14,000 people in Europe annually. Anal cancer is more sensitive to radiotherapy, and previous clinical trials have shown that a combination of radiotherapy and chemotherapy can replace the need for major surgery and a permanent colostomy. However, the current standard approach results in high rates of short and long-term side effects.
Now, five pivotal studies presented at ESTRO 2025, the annual congress of the European Society for Radiotherapy and Oncology, showcase how radiotherapy is reshaping this landscape. From reduced-dose treatments to cutting-edge combinations with immunotherapy and chemotherapy, these innovations offer safer, more effective, and organ-preserving alternatives to traditional surgery.
1. Shorter, Lower-Dose Radiotherapy for is a Highly Effective Treatment for Early-Stage Anal Cancer
The ACT4 PLATO trial (1), led by Professor David Sebag-Montefiore, has demonstrated that a reduced-dose, shorter-course highly focused radiotherapy technique (IMRT) offers excellent tumor control with fewer side effects for early-stage anal cancer. The randomized phase II trial, conducted across 28 UK sites, showed similar efficacy and late toxicity levels using a reduced-dose IMRT regimen over 4.5 weeks and standard-dose IMRT over 5.5 weeks.
“Our results support moving toward shorter, more personalized radiotherapy,” said Professor Sebag-Montefiore. “This approach reduces the treatment burden for both patients and healthcare systems.” Ø Read the press release on the ACT4 PLATO trial
2. Radiotherapy Alone and Radiotherapy Combined with Chemotherapy both Enable Patients to Avoid Surgery for Rectal Cancer
The STAR-TREC study (2) has shown that organ-preserving strategies are feasible for patients treated with radiotherapy alone as well as for patients treated with radiotherapy and chemotherapy. Among 344 patients at 37 international sites, 80% of those treated with chemoradiotherapy and 61% of those treated with radiotherapy alone could be spared surgery at one year.
“Avoiding surgery helps preserve bowel function and quality of life,” said Prof Dr Corrie Marijnen, of the Netherlands Cancer Institute. “This study shows that radiotherapy-based strategies (whether alone with more intensive treatment course, or combined with chemotherapy) can be a viable alternative for many patients.” Ø Read the press release on the STAR-TREC trial
3. Immunotherapy-Radiotherapy Combo Eliminates Cancer in Two-Third of Patients in UK Trial
PRIME-RT, a trial conducted across the UK, found that 67% of evaluable patients receiving a short-course of radiotherapy, meaning only 5 outpatient sessions (no overnight stay) of radiotherapy, combined with immunotherapy had a complete response, meaning no signs of cancer remained.
“By combining immunotherapy with radiotherapy, we are seeing higher response rates than expected, especially with short-course radiotherapy," said Professor Campbell Roxburgh, from the University of Glasgow, UK.
4. Combining Radiotherapy with Immunotherapy and Chemotherapy for Better Organ Preservation
Similarly, in the STELLAR II trial from China, immunotherapy added to short-course radiotherapy and chemotherapy increased complete disappearance of the tumor to 45.5%, compared to 25% with standard treatment.
“By combining immunotherapy with short-course radiotherapy and chemotherapy, we may be able to improve survival rates and, crucially, help more patients avoid invasive surgery and its long-term effects,” said Professor Jing Jin, from the National Cancer Centre, China.
5. Short-Course Radiotherapy with Chemotherapy Boosts Long-Term Survival
The phase III STELLAR trial tracked 591 patients in China with locally advanced rectal cancer over five years. It found that short-course radiotherapy followed by chemotherapy improved survival by 8.4% compared to standard long-course chemoradiotherapy—with no negative impact on anorectal function or quality of life. "This could be a game-changer for patients, offering a faster, equally safe, and potentially more effective option," said Dr Jing Jin from the National Cancer Centre in China.
A New Paradigm in Rectal Cancer Treatment
Together, these five studies demonstrate the transformative potential of radiotherapy as a curative and organ-preserving treatment. As new data emerges, personalized radiotherapy strategies are offering patients safer, effective alternatives to surgery.
“These breakthroughs represent a major step forward,” said Professor Guckenberger. “By leveraging advanced radiotherapy strategies, we are not only improving survival rates but also prioritising quality of life for patients worldwide.”
With these findings set to influence global clinical guidelines, the future of rectal cancer treatment is moving decisively toward combined radiotherapy-driven, organ-preserving solutions.